Judgment of the General Court (Fifth Chamber, Extended Composition) of 20 December 2023.#enercity AG v European Commission.#Competition – Concentrations – German electricity and gas markets – Decision declaring a concentration compatible with the internal market – Concept of ‘single concentration’ – Definition of the market – Assessment of the effects of the transaction on competition – Manifest errors of assessment – Duty of diligence – Misuse of powers.#Case T-65/21.